The present invention generally relates to an LED grow light system. More specifically, the present invention relates to a full spectrum LED grow light system for producing a light output spectrum comparable to the sun at a relatively efficient and low power input.
The sun provides the vast majority of energy required for photosynthesis in plant growth on Earth. That being said, the sun is still not necessarily the most efficient light source for growing particular types of plants at least in part because the energy emitted by the sun cannot be readily controlled and/or regulated based on plant specific grow cycles, i.e., the light energy wavelengths emitted from the sun cannot be fine-tuned to optimize plant growth characteristics. As an example, FIG. 1 is a sun light spectrum graph 20 illustrating the spectra of light output from the sun at various wavelengths and intensities under various conditions during the day. More specifically, the vertical scale illustrates the relative light output intensity from the sun at various wavelengths and under different meteorological conditions as identified in the graph 20. Direct sunlight during blue sky conditions (i.e., no overcasts) has the highest intensity, at least generally for wavelengths in about the 350-475 nanometer (“nm”) range. While the light output from the sun includes a relatively broad spectrum of wavelengths having a relative spectral power output fairly consistently high as illustrated in FIG. 1, it is known that plants typically do not actually use the entire spectrum of sunlight emitted by the sun and that specific wavelengths/intensities may be more desirable than others. Thus, simply replicating the spectral power intensities of the sun, as shown in FIG. 1, in a grow light system is energy inefficient.
In the last several decades, High Pressure Sodium (“HPS”) lamps have been used extensively as plant grow lights for indoor and outdoor plant growing systems to replace or supplement natural sunlight. In this respect, HPS lamps are proven to be some of the best available artificial lighting systems for plant growth because of the relatively high output intensity within certain visible light spectrums. Moreover, HPS lamps have a relatively low price, relatively long life, relatively high photo-synthetically active radiation (“PAR”) emission, and a relatively high electrical efficiency. Although, one drawback is that HPS lamps are not necessarily optimal for promoting photosynthesis and photomorphogenesis since HPS lamps have limited spectral light output intensities at certain wavelengths. For example, FIG. 2 is an HPS light spectrum graph 22 illustrating the relative intensities of visible light emitted from an HPS lamp. As shown, the HPS lamp has an energy intensity strongest around the orange-red part of the spectrum, i.e., at wavelengths of about 560-620 nm, with a peak 24 near the 600 nm wavelength. Such strong light intensities in this range tend to stimulate plant hormones to start budding and flowering, but do not necessarily promote desired growth. Thus, one disadvantage is that continued exposure to such high intensities in the orange-red part of the spectrum (i.e., wavelengths of about 580-620 nm) can result in excessive leaf and stem elongation due to the unbalanced spectral emission intensity from the HPS lamp in this range, and especially relative to other absorption peaks of the plant. Thus, while HPS lamps have been widely used, plant growth under HPS lamps may be less than optimal. Even so, given the past success of HPS lamps operating as plant grow lights, it may still be desirable to somewhat replicate the HPS lamp light output spectrum in more energy efficient systems, such as LEDs.
In recent years, LED lighting technology has matured within the lighting industry such that advancements in LED architecture have resulted in significantly reducing manufacturing costs, increasing LED efficiency, and creating an overall more robust LED light design better suited for use in plant grow light systems. In this respect, it may now be feasible to replace HPS lamp-based plant grow light systems with LED-based plant grow light systems in the horticulture business to lower the Total Cost of Ownership (“TCO”), such as lowering the cost of electricity (i.e., LEDs tend to be more energy efficient than HPS lamps), lowering the cost of air conditioning (i.e., LEDs tend to generate less heat and require less cooling to maintain adequate operating temperatures relative to HPS lamps), lowering the cost of the lamps themselves, and increasing lamp longevity (i.e., decreasing the replacement rate in view that LEDs have a longer projected lifespan). Although, one major drawback of using LEDs as a plant grow light is that the spectrum of the LED output is different than the output of sunlight and different than most acceptable artificial HPS lamps used for plant grow light applications. For example, LED grow light designs manufactured specifically for the horticulture market use blue LEDs (e.g., at wavelengths of about 420-480 nm) and red LEDs (e.g., at wavelengths of about 620-780 nm). To this end, the green spectrum (e.g., at wavelengths of about 500-580 nm) is commonly omitted from LED plant grow lights since the belief within the industry is that green light is reflected by the chlorophyll in the leaves and thus not absorbed by the plant. Thus, important aspects of robust plant growth are lost since wavelengths between the blue spectrum and red spectrum (e.g., within the green or yellow spectrums) are disregarded and commonly omitted from LED grow lights. HPS lamps, on the other hand, have relatively stronger (yet not optimal) green spectrum intensities in the 500-580 nm wavelength range as shown, e.g., in FIG. 2. Although, HPS lamps are more expensive and have a relatively shorter life when compared to LED lights, and HPS lamps are also not necessarily environmentally friendly because they contain mercury, and, importantly, the spectrum of the HPS lamp cannot be tailored to meet the various spectral needs of different plants.
One benefit of an LED grow light is that there are a wide number of available LEDs that generate light output at custom wavelengths. Although, mimicking the sun or an HPS lamp in an LED grow light is not as simple as aggregating several differently colored industry standard LEDs having different light output wavelengths because the resultant spectrum is not exactly similar to that of the sun light spectrum graph illustrated with respect to FIG. 1 or the HPS lamp light spectrum graph 22 illustrated with respect to FIG. 2. For example, FIG. 3 is a tri-LED light spectrum graph 26 illustrating the relative radiant power of three off-the-shelf LEDs having different color temperatures (“CCT”) and different color rendering indices (“CRI”). As shown, even the lowest 2,200K CCT LED does not have a spectrum that matches the HPS lamp light spectrum graph 22 as closely in intensity in the blue spectrum (e.g., at wavelengths of about 420-480 nm)—the relative radiant power intensity is too high. It becomes necessary to either increase the amount of the orange/red light (e.g., at wavelengths of about 580-620 nm) to compensate for the relatively high intensity in the blue spectrum; or decrease the amount of blue light so the LED light output is similar to that of the HPS lamp. Continuing to lower the CCT of the LED further lowers the amount of blue light, but at a penalty in lowering the efficiency of the LED. Thus, current LEDs known in the art are ineffective in grow light applications, especially when compared to HPS lamps.
In another example, FIG. 4 illustrates an octo-LED light spectrum graph 28 illustrating the relative radiant power of eight standard off-the-shelf LEDs made with different phosphor materials, each with a different center light output wavelength such that the output spectrum can be tailored to the desired wavelength. Various combinations of such phosphor materials may provide for different color outputs based on the compositions of the phosphors. Here, to add more of the orange/red spectrum to the LED lighting system, additional LEDs that emit output light in more of the amber, orange/red, and/or red spectrum may be added to help better mimic the spectrum of that of the HPS lamp. This is accomplished chiefly by increasing the output intensity of the LEDs having the orange/red wavelengths, such as relative to the blue spectrum light output. Even so, each of the LEDs produces sharp peaks uncharacteristic of the sun light spectrum graph 20 or the HPS lamp light spectrum graph 22, thus producing less than optimal plant growth results. As a result, LED grow lights tailored to have peak output wavelengths in the same or similar region as an HPS lamp may tend to be more efficient and effective in applications for growing plants, unlike the aggregation illustrated in FIG. 4, especially when combined with light output having intensities at other wavelengths along the spectrum (e.g., at wavelengths of about 380-780 nm) similar to the sunlight spectrum graph 20 and/or the HPS lamp light spectrum graph 22. Such LED grow lights may provide advantages over the sun and well-proven HPS lamps, as discussed in more detail herein.
There exists, therefore, a significant need in the art for an LED grow light system that optimizes the light output spectrum for plant growth through deployment of multiple differently colored LEDs deigned to replicate the sun and/or HPS lamp light output intensities at wavelengths conducive for plant growth at a relatively low input power, and includes an enhanced cooling system that includes a heatsink with a plurality of heat dissipating fins and a set of heat transfer pipes drawing heat energy away from a circuit board with the heat generating LEDs thereon to a series of heatsink fins positioned for convection cooling within a vented heat sink housing. The present invention fulfills these needs and provides further related advantages.